The Buddha's doctrine, in essence, rests upon the idea of "knowing and regarding reality as it is". That means one should know the true facts about this earthly life and look at it without making excuses and regulate ones daily life according to this knowledge and standpoint.

The idea that there is nothing but hardship in this world and that even pleasures end in hardship is one of the significant points of Buddhism. Some might say that this notion of recognising this life as hardship cannot be anything but pessimism [http://en.wikipedia.org/wiki/Pessimism]. But that is not right. The idea is this:

In this present life there are both pleasure and hardship. It is shallow to try to regard it as entirely please. What one regards as pleasure will cause suffering when it ceases to exist. In other words we may call it a hardship that exists in the guise of pleasure. Therefore this life must be regarded as consisting entirely of hardship. Yet one should not lament this. If one is ignorant of the fact that pleasure can cause hardships, one will be disappointed when that fact presents itself.

The Buddha teaches that one should regard hardship as hardship, accepting it as a fact and not opposing it. Hence the Buddha emphasises the importance of perseverance, fortitude and forbearance.

In short - there are both pleasures and hardships in this life, but one must not be discouraged when hardship comes or loose oneself in rapture and joy when pleasure comes. Both must be taken with caution and one must attack doubt of this fact [or 'Truth'] with all one's might. Hence the Buddha emphasises the importance of bravery and diligence.

When the Buddha's idea on reality develops further along its path, it becomes Buddhist philosophy. To realise it in the actual life of living men and women is the religious side of Buddhism.

The Buddha organised these ideas into The Fourfold Truth as follows:
1. Life consists entirely of suffering
2. Suffering has causes (these two are the description of reality)
3. The causes of suffering can be extinguished
4. There exists a way to extinguish the causes (the last two express the ideal)

Contemporized: Life is suffering. There is a cause of that suffering. There is a way out of that suffering. That way out is the Noble Eightfold Way.